Thanks for the update...
Is something like this what you installed?
https://www.rockauto.com/en/moreinfo.php?pk=12710637&cc=1031184&pt=17507&jsn=981
That compressor in the link looks very different from the R4 pancake that comes with the early 90's.
If what you installed looks like the pic in the link I'm wondering if it's a direct bolt on to the OEM bracket?
Edit: I just realized you're the OP of this thread... and after seeing the video you linked, it sure looks like a pancake compressor. lol
I guess rock auto went with a generic picture of a random compressor in that link? If you have any other info that would be helpful let me know.
I see that PlayingwithTBI gave a suggestion on wiring the high pressure switch. I don't have a max air/recirculate button... but
I'm gonna see if I can find a good post on rewiring that.